Typing on a keyboard is the most common and efficient way for a user to enter data into a computer system. For this reason, computers of all sizes use a form of alphanumeric keyboard to allow a user to enter data. As ever more powerful computers are compressed into smaller sizes, keyboard technology has changed. Examples abound, such as the miniaturized keyboard of the BLACKBERRY® handheld, and the virtual keyboard which users can call up on an iPAD® tablet computer.
These and other keyboards for small computers, especially keyboards associated with mobile computers and most especially those on tablet computers and other computers with touch-screen technology, are less effective than traditional computer keyboards because they are not optimized for touch typing.
Touch typing as we know it today was invented around 1888, yet is still the fastest and most accurate way of entering data into a computer system. A touch typist memorizes the location of the keys on the keyboard and uses muscle memory instead of sight to type. Touch typing can be performed while typists focus vision and attention on things other than the keyboard.
The touch typist places eight fingers on specific keys in the home row, rests them there when not typing, and returns to them while typing in order to re-orient their fingers. These keys are referred to as the home row rest keys. On a standard QWERTY keyboard, these are “ASDF” for the four left fingers and “JKL;” for the right four fingers. The typist actuates a home row rest key by striking the key in a generally vertical direction.
For the sake of clarity a North/South, East/West orientation reference system is used in this document. The northern most alpha row of a QWERTY virtual keyboard is designated row 1 and at least contains the letter keys “Q”, “W”, “E”, “R”, “T”, “Y”, “U”, “I”, “O”, “P.” Row 2, the next row south of row 1 is also referred to as the “home row” and contains at least the letters “A”, “S”, “D”, “F”, “G”, “H”, “J”, “K” and “L.” Row 3, the next row south, contains at least the letters “Z”, “X”, “C”, “V”, “B”, “N”, and “M.” Row 4 is also referred to as the “space-bar row.” The directions “vertical”, “straight up”, “straight down”, or “normal” are used synonymously and interchangeably to describe trajectories essentially perpendicular to a plane defined by the entire keyboard layout, or in the case of digital tablets, approximately perpendicular to the glass touch-screen. Note that this is simply a labeling mechanism—the present invention is not dependent on the keyboard layout on the underlying virtual keyboard. It functions identically for a QWERTY, AZERTY, Dvorak, numeric, split keyboard, or any other keyboard layout used for touch typing.
A touch typist strikes the other keys on the keyboard at many different lateral angular trajectories in addition to straight down. All of the possible finger trajectories that occur in touch typing are referred to as the touch typing finger trajectories. After striking the key, the finger then returns to its place on the home row. The typist's thumbs hover over the space bar and strike it vertically. Touch typists can actuate multiple keys in parallel (that is, press down on one key while one or more other previously actuated keys are still depressed). The requirement for a keyboard to allow, recognize and distinguish among multiple nearly simultaneous keystrokes is referred to as “n-key rollover.” Thus, a keyboard design that allows the system to distinguish a second key stroke while one other previously actuated key is still depressed has “2-key rollover,” and a keyboard design that allows the system to distinguish between one key while two other previously actuated keys are still depressed has “3-key rollover.”
An optimal keyboard design for the vast majority of typists has 4-key rollover, allowing the system to account for and recognize a fourth key being depressed while two other previously actuated letter keys plus the SHIFT key are still depressed.
The touch typist automatically re-aligns his or her fingers to proper placement on the keyboard (also referred to as finger alignment) through subtle tactile cues gained while typing, such as the outer edges of the key tops on all rows or small nubs over the home row keys that the index fingers rest on (typically the “F” and “J” keys of a standard QWERTY keyboard). Some keyboards have spherical or cylindrically concave or convex surfaces on the top surfaces of each key top that also provide tactile finger alignment feedback.
People who have not learned to touch type typically use a “hunt and peck” method of typing that is performed with two or more fingers. As the name implies, the typist simply hovers his or her fingers over the entire keyboard and strikes keys as needed. Since the “hunt and peck” typist moves the finger directly over a key before striking it, most key presses are approximately straight down. “Hunt and peck” typists must keep sight and attention focused on the keyboard. They must actively support the weight of their fingers during the periods they are hovering.
In general, touch typing is significantly faster and more accurate than “hunt and peck” typing, because the touch typist's fingers travel shorter distances to key actuation, and the touch typist uses many more fingers simultaneously or in quick sequence. Effective touch typists can focus attention on sources other than the keyboard while typing. In fact, the act of consciously thinking about each key and possibly looking for it slows many typists down and can even adversely affect typing accuracy.
Keyboards for touch typing must be large enough to allow the typist to place eight fingers on the home row, with four fingers of each hand located on keys immediately adjacent to each other. For the majority of the adult population, this requires a keyboard with a lateral key pitch (East/West distance from the center of one key to the center of the adjacent key) of 19-19.5 mm. Keyboards with smaller key pitches become increasingly more difficult to use for touch typing the smaller the pitch becomes. Typing speed goes down and error rates go up as the pitch gets smaller.
The home row rest keys must provide enough resistive force (vertical support) to allow the typist to comfortably rest his or her fingers on these keys. This requires approximately 10 g-20 g of resistive force. At the same time, these keys must be responsive enough to be easily actuated when the typist consciously decides to type. Because the touch typist only rests the stationary weight of their fingers on eight keys in the Home Row, a keyboard optimized for a highly skilled touch typist does not require other keys to have resting resistive force. Existing mechanical keyboards and keyboard overlays, however, provide the same resting resistive force on all keys.
Touch typing is a very dynamic activity. The average typing speed of a trained touch typist is 38-40 words per minute (wpm). Highly skilled typists achieve 100-120 wpm range. Thus, keystrokes occur at average rates ranging from 300-100 ms with peak rates at even shorter time intervals. In order to achieve these rates, a typist must rapidly accelerate fingers at the start of each keystroke. Left unchecked, this acceleration would continue through the full length of key travel causing the typist's finger to hit the end of key travel (also known as “bottoming out”) at a high speed and with maximum momentum and kinetic energy. Keyboards which permit “bottoming out” force the typist to expend a large amount of time and energy recovering, resulting in slower typing performance and increasing the likelihood of induced repetitive stress injury. Keyboards designed for optimal touch typing must decelerate the typist's finger after the key press has been initiated, through the length of travel of the key, and ideally before the finger reaches the end of key travel. Thus, even if the finger does reach the end of travel, the deceleration provided by the key switch will significantly reduce the finger's impact when it reaches the end of travel. This enables the typist to easily reverse direction with the least amount of expended energy.
Finally, a keyboard optimized for touch typing gives the typist's finger a spring-back force on the return that helps accelerate the typist's finger in the reverse direction.
A keyboard optimized for touch typing also provides a tactile cue that a key has been successfully actuated. This is typically done by varying the rate of increase of resistive force or decreasing the resistive force just before the key's actuation point. By necessity this cue is subliminal and is mainly in place to assist people touch typing at high speeds: keystroke rates of 50 ms-300 ms are so fast that conscious reactions to actuation cues are not possible.
Touch typing performance is also affected by the pressure required to actuate a key and the length of key travel before actuation occurs. The more pressure that is required over a longer distance, the greater the work that is required of the typist and therefore the slower typing will be. However, too little pressure and too short a key stroke would not give the typist sufficient tactile feedback and finger cushioning, nor would it allow the user to comfortably rest fingers on the home row without inadvertently depressing a key to the point of accidental actuation.
Finally, typists have a wide range of preferences in the characteristics of a keyboard, based on their level of typing skill and personal preferences. For example, a typist who is new to touch typing might prefer a keyboard with higher resistive force through the length of key travel and a more pronounced pre-actuation cue in order to more effectively learn. A fast, experienced typist might prefer a low travel keyboard that has minimal resistive force but a high spring-back force that allows typing fastest. Some typists prefer one style of pre-actuation feedback; other typists prefer a different style, etc.
Today, there are three keyboard technologies in common use for touch typing:                Rubber domes. The key cap is connected by a plunger to a rubber dome. The rubber dome collapses at a point in the downward travel of the key and snaps back up when finger pressure is released. This produces the tactile feel and actuation cueing for this type of keyboard.        Scissor switches. These are a variation of rubber dome keyboards that allow for greatly reduced travel. They are primarily used in laptop computers. The rubber dome still produces the tactile feel and actuation cueing.        Mechanical switches. These use springs, levers and indents to produce their tactile feel and cueing.        
Conventional keys are constructed with a hard key cap that extends over the edges of the key and is tightly coupled to the plunger tied to the underlying mechanism within the body of the key switch. Even though touch typist's fingers often hit the non-home row rest keys at an angle, the finger's angular trajectory is converted to vertical trajectory by the constrained coupling of the key cap to the key's vertically oriented plunger. Therefore, all mechanical keys actuate vertically. Even flexible, waterproof keyboards with rubber key caps and sidewalls have thick, hard key caps, and work in this manner redirecting non vertical finger trajectories to vertical key travel.
The primary characteristics of keyboards relevant to optimization for touch typing can be characterized in the following categories and ranges:                Key travel. Ranges from 3.5 mm-4 mm for “full travel” desktop keyboards, and 2 mm-3 mm for laptop and subnotebook computers, due to the severe height constraints on keyboards for those devices.        Key actuation force. Ranges from approximately 30-70 grams.        Finger resting resistance. Ranges from approximately 10-20 grams.        Tactile pre-actuation cueing. The existence of a tactile pre-actuation cue is optimal.        Deceleration. Decelerate a finger over the length of key stroke to the point where the finger can be reversed before reaching end of travel is optimal.        Spring-back. Ranges from 5-50 grams.        
FIG. 1 shows a typical graph of actuation force as a function of key travel distance (aka a force displacement curve) for a full-travel mechanical key that is used for touch typing. The force curve 12 is linear for approximately the first 1.0 mm of travel, then increases rapidly, forming a pressure point 10 that the typist must overcome. This point is known as the pre-actuation cue. This is followed by a steep reduction in force 14 which only begins to increase just short of the actuation point 11 of the switch. The pre-actuation cue will cause the typist to experience a tactile “bump” when they strike the key and travel past the pressure point, which provides the subliminal indication that the key will be successfully actuated. The decrease in resistive force 14 immediately after the pressure point ensures that the typist's finger will always pass through the actuation point 11 of the key switch, which in this example occurs at approximately 2 mm of travel. The force curve returns to linear 15 following the actuation point; this decelerates the typist's finger after actuation has occurred. The end of key travel 16 for this key is at 4 mm, where the force curve goes essentially vertical 17. If the typist's finger is still moving forward at this point, it will encounter the end of travel and be stopped. An effective high speed typist will be able to reverse finger direction before hitting the end of travel, or will hit the end of travel with much reduced force, compared to the force they would hit it with if the key did not provide deceleration. The lower line on the graph 13 shows the force displacement curve when the typist's finger is travelling in the reverse direction (up—away from the key switch). The resistive force of the key in this direction generally acts as an accelerator of the reverse motion of the finger, providing a spring-back effect.
FIG. 2 shows a typical force displacement curve 20 for a key switch with a linear force curve. Since the typist's finger is still accelerating when it first lands on the key, the key's linear resistance will feel low. As the resistance rate increases linearly throughout the length of travel, the typist receives no tactile feedback or pre-actuation cueing. The act of “bottoming-out” at 4 mm travel 21 would be the first indication to the typist that the key is actuated 11. Therefore, key switches of this type cannot be used for effective touch typing; instead, they are typically used by computer gaming enthusiasts, where repeated, fast actuation of a small number of keys is paramount.
FIG. 3 shows a typical force displacement curve 30 for a mechanical key switch that has a graduated linear force curve, where the slope increases in stages over the range of key travel. An example of this kind of key switch is shown in the U.S. Pat. No. 4,529,849. This type of key switch is used for touch typing. The first segment of travel 31 has a slope similar to the tactile actuation key, and works in the same manner. But then the slope of the curve increases significantly 32. The typist feels this as an increase in the rate of deceleration of their finger which gives him a subliminal tactile cue that actuation is imminent and it is time to start reversing. At this point the typist's finger still has enough forward momentum to reliably pass through the key's actuation point 11. As soon as the actuation point 11 is passed, the linear rate of force increases to an even higher rate 33 further decelerating the typist's finger. This makes it less likely that the typist will “bottom out.” Forward and reverse force displacement curves 30 are approximately identical. Spring-back force for this key is highest at the point of finger trajectory reversal 34. This results in a “lively” feel.
The force displacement curves 12, 30 shown in FIGS. 1 and 3 exhibit a very sharp approximately vertical slope 18, 35 at the early moments of finger contact with the key top travel leveling down to a linear approximately 10 cN/mm slope 19, 31. The typist's finger encounters enough resistive force for rest support somewhere along this initial slope and well before the finger reaches the actuation point 11 at significantly higher resistive force and travel. This common characteristic is essential to and provides the typist with the ability to rest their fingers on the home row keys.
FIG. 4 shows a typical force displacement curve 40 for a representative laptop rubber dome scissor switch that is used for touch typing. This key switch has 2 mm of key travel, substantially shorter than the full-travel mechanical switches shown in FIGS. 1 and 3. Since tactile actuation cueing is a very desirable and expected feature, the pre-actuation portion of the force curve 10 has been left largely unchanged while the post-actuation portion 41 has been significantly reduced, compared to the mechanical switch shown in FIG. 1. Note that the actuation point 11 is very close to the end of key travel 42 for these types of key switches.
Touch sensing technology has been available since the 60s, but the first commercially available touch screen, e.g. FIG. 5A, which combines a transparent touch sensing panel 50 on top of a Plasma, CRT, LCD or OLED display panel 51, was developed in 1974 by Elographics. The touch detection technology used by Elographics is known as analog resistive. It is a pressure sensing technology: touch panels are composed of two flexible sheets 52, 53 coated with an electrically resistive material and separated by an air gap 54 or microdots 55, as illustrated in FIG. 5A. When pressure is applied to the surface of the touch screen 56, the two sheets are pressed together 58, and make electrical contact, see FIG. 5C. One sheet supplies the x position, the other sheet the y position of the touch, as measured by the current resistance values.
Analog resistive technology requires substantial activation pressure to register a touch, on the order of 50-100 grams. The actuation pressure must be applied for the entire duration of the actuation period, as illustrated in FIGS. 5A, 5B and 5C. FIG. 5A shows the point where the user's finger 57 first touches the surface 56 of an analog resistive touch screen. Even though the user's finger has already made contact with the hard surface 56 of the touch screen, no detection of the user's finger has yet occurred. FIG. 5B shows that the user's finger 57 has now depressed the touch screen to the point where there is partial contact 59 between the top 52 and bottom 53 conductive layers. But touch panel contact measurements are not stable at this point; the user must push through to full contact 58 in order to generate a reliable steady actuation, as shown in FIG. 5C. Because of the force required, a pressure concentrator (also known as an energy director), such as a stylus or nib on the bottom of a key is often needed in order to enable the user to easily actuate an analog resistive touch screen. Analog resistive is a single-point touch detection technology—that is, it is only able to detect one location or point on the touch screen at a time. If multiple touch points are present, an erroneous location is reported.
Analog resistive technology was used in the first commercially available smart phone, the IBM/Southwest Bell Simon, which was released in 1992. Analog resistive is still the most popular touch screen technology in use today.
The Simon had a virtual keyboard—that is, an alphanumeric keyboard implemented in software that uses a touch screen to display the keys and senses when the user taps on a key to actuate it. Many subsequent analog resistive touch screen devices have also implemented virtual keyboards. However, these can only be used for “hunt and peck” typing, not touch typing, because of the following shortcomings:                In order for an analog resistive touch screen to reliably register key actuation, key strokes must be “bottomed out” with significant force and held down for a period of time.        Single-point touch detection doesn't allow simultaneously holding down the shift key and striking another key, nor does it allow for multi-key rollover.        
Therefore, this approach never achieved significant commercial success. In 1993 AT&T released the EO Communicator, a tablet-sized device with a single-point, pen-based touch screen and an operating system, PenPoint, designed specifically for pen input and handwriting recognition as the primary input mechanism. Microsoft subsequently released a pen-based version of the Windows operating system with the same general characteristics, and many manufacturers began producing pen-based tablet devices with touch screens optimized for styluses. For the next 17 years, pen-based devices dominated the tablet-sized device space. Virtual keyboards on these devices could not be used for touch typing, and handwriting recognition was inaccurate and very time consuming to use. These devices as a whole served a relatively small niche market and never achieved broad commercial success, in large part because of their inadequate approach to input.
A better solution for input on tablet devices would be if users could utilize their existing typing skills and be able to enter data with the same speed and accuracy as they do on a physical keyboard. At the same, this mechanism would need to maintain the small size and weight advantage that a tablet computer had over a laptop computer.
In order to facilitate this sort of solution, a different touch screen technology needs to be used—one that supports multi-point (the ability to detect any number of simultaneous touches) and one that doesn't require force to register a key stroke. Proximity-based touch screen technologies that detect the user's fingers when they are close to the touch screen without actually touching it, meet these requirements. Several touch screen technologies provide both multi-touch and proximity-based detection.
For example, surface acoustic wave (SAW) technology uses ultrasonic transducers and receivers to set up a field of ultrasonic sound waves over the touch panel. When the panel is touched, a portion of the wave is absorbed by the user's finger. This change is used to register the position of the touch event. However, SAW technology requires high power and a thick bezel to house the transducers. It is therefore not usable for mobile devices.
Vision-based optical systems use an infrared video camera mounted underneath a hard, transparent plate to detect the presence of objects touching the surface of the plate. Infrared light is used to illuminate the plate, either by injecting it into the side of the plate or by illuminating the underside of the plate with infrared light from below. Objects touching the surface change how the infrared light is reflected; these changes are measured with a video camera. However, given their size and power requirements, they cannot be used in mobile devices.
Digital resistive touch panels share the same manufacturing process as analog resistive. Unlike analog resistive, they support multi-touch, since the conductive material covering the touch panels is etched into a pattern of rows on one panel and columns on the other. When pressure is applied to the top panel it bends slightly, creating electrical contact between the two layers at the touch point. In effect, there is a small micro-switch at each intersection point in the grid. The rows and columns are continuously scanned, looking for switch closings. Digital resistive technology requires significantly less force to register a touch than analog resistive, but it is still a pressure-based technology with the drawback of requiring a key stroke to “bottom out” on the touch screen's surface.
Capacitance touch technology is proximity-based. It utilizes the fact that the human body is a conductor in order to change the characteristics of an electrostatic field. Surface capacitance technology is the simplest form of capacitance touch sensing. It consists of an insulator such as glass, coated on one side with a transparent conductive layer. A small voltage is applied to the conductive layer, resulting in a uniform electrostatic field. When a person finger touches the surface of the screen, the screen's electrostatic field is distorted, which can be measured as a change in capacitance. However, surface capacitance technology only detects single-point contact not multiple point contact as required for touch typing, such as using a “shift” key along with a letter key to indicate a capital letter.
Projected Capacitive technology (Pro-Cap) is a recent refinement of capacitive technology that utilizes an X-Y grid that is formed by etching one or two transparent conductive layers to form a grid. The grid is repetitively scanned in order to detect changes in capacitance across the grid. Pro-Cap makes use of the fact that most conductive objects are able to hold a charge if they are very close together. If another conductive object, such as a finger, comes close to two conductive objects, the charge field (capacitance) between the two objects changes because the finger's capacitance “steals” some of the charge. The E-field lines are “projected” beyond the touch surface when a finger is present, thus touch detection occurs in a proximity zone that starts slightly above the touch screen surface and therefore does not require the touch screen surface to be touched in order for a finger to be registered.
There are two types of Pro-Cap technology: self capacitance and mutual capacitance. Self capacitance systems serially scan each row and column in the grid and therefore only provide single-point detection.
Mutual capacitance systems scan the intersections of each row and column and measure the capacitance at each intersection. Therefore, mutual capacitance systems are multi-point.
In addition to appropriate touch screen technology, the tablet device would need to be large enough for a virtual keyboard with a lateral key pitch appropriate for touch typing, as described above. This system would also need to have a sophisticated virtual keyboard that took full advantage of this touch screen technology and handled all the requirements of touch typing.
In 2004, Apple Computer filed U.S. Pat. No. 7,663,607. This patent describes a mutual capacitance Pro-Cap technology that is appropriate for touch typing. Additionally, U.S. Pat. Nos. 7,479,949 7,602,378, 7,614,008 and 7,844,914 describe a virtual keyboard designed to work with this type of touch screen technology. In 2007 Apple released the iPhone. This was the first time that a proximity-based, multi-touch device with a matching virtual keyboard as described in these patents became generally known in the industry. In March of 2010 Apple released the iPAD®, a tablet-size device with a 9.7″ diagonal touch screen that utilized equivalent Pro-Cap technology. The iPAD® has a virtual keyboard as described in U.S. Pat. Nos. 7,602,378, 7,614,008 and 7,941,760. These show the characteristics of virtual keyboard software in modern touch screen devices.
The virtual keyboard described in these patents has sophisticated software features designed to optimally handle touch typing. For example, properly handling the touch typing finger trajectories on a Pro-Cap touch screen is outlined in U.S. Pat. No. 7,812,828. Another important feature is that the virtual keyboard extends the touch detection area of a key into the visual border that visually separates the keys. Therefore, all locations on the virtual keyboard will register a key press. Also, the virtual keyboard handles the case where a finger strike overlaps two or more key boundaries by analyzing the shape of the multiple touch screen points actuated by the pad of the user's finger to determine the nearest key. These virtual keyboards have an additional layer of software that provides automatic correction of mistyped words, partly based on an analysis of adjacent letters on the keyboard. For example, if the user enters the word “oace” instead of “pace” on a QWERTY virtual keyboard, there are four possible corrections—“face”, “lace”, “pace”, “race.” However, the proximity of the “o” key to the “l” and “p” keys allows the virtual keyboard software to eliminate the “face” and “race” possibilities. The choice between “lace” and “pace” will be made based on whether the key stroke that registered the “o” was closer to the “l” key or the “p” key. Finally, these virtual keyboards also work at the sentence level. They automatically capitalize the first word of a sentence, and will automatically add a period to the end of a sentence if two spaces are entered to indicate the start of the next sentence.
The iPAD®'s 9.7″ touch screen size allows for a virtual keyboard with 18 mm key pitch. This is smaller than the ideal 19 mm-19.5 mm key pitch of a full-size mechanical keyboard. However, the virtual keyboard software makes up for this by expanding the touch areas and intelligently handling overlapping touches in a way that a physical keyboard cannot, as described above.
Thus, the iPAD® was the first touch tablet device that met the basic hardware and virtual keyboard software requirements needed to support optimized touch typing on a touch screen device. This has proven to be a popular approach with users, resulting in considerable commercial success for the iPAD®. The iPAD® achieved a market share of approximately 90% in its first year of availability. A host of competitors to the iPAD® that also meet basic touch typing requirements emerged about a year after the iPAD® launch—for example, the Motorola XOOM®, the Samsung GALAXY TAB 10.1® and the HP TOUCHPAD®. These devices have multi-point Pro-Cap touch screens, sophisticated virtual keyboards and screen sizes large enough for virtual keyboards that can support touch typing.
Even though these devices have the necessary touch screen and virtual keyboard support, touch typing is still severely compromised. The issues are:                1. Typists cannot rest their fingers on the home row of the virtual keyboard displayed on the touch screen, since this would immediately trigger multiple unwanted key actuations.        2. There is no mechanism for decelerating the typist's fingers before they impact the touch screen. Given the ballistic nature of high speed touch typing, typist's fingers strike the hard touch screen at a high rate of speed with every key stroke. This can result in significant discomfort for the typist and increases the likelihood of repetitive stress injuries over time. This is especially ironic, since proximity-based touch screens such as Pro-Cap can detect the typist's finger prior to it even making contact with the surface of the touch screen.        3. It is difficult for touch typists to reliably ascertain that they have correctly actuated a key when typing rapidly on these devices, since there is no subliminal tactile cue prior to actuation. The only tactile cue the user receives is from impact with the touch screen. This causes a significant decrease in typing speed and increases error rates.        4. There is no spring-back when the typist reverses their finger after completing a stroke. This results in slower typing speeds and less comfort while typing.        5. There are no tactile reference points for detecting the location of keys on the virtual keyboard. Thus, it is very easy for a touch typist's fingers to inadvertently drift off the key locations over time during typing. In order to compensate, typists must look down at the keyboard at all times. This eliminates one of the major benefits of touch typing—allowing the typist to focus their attention on something other than the keyboard while typing.        
Note that these issues apply to any device with a touch screen and a virtual keyboard capable of touch typing, not only tablet computers. For example, accountants and others who focus on numeric data entry, touch type on the numeric keypad found on many mechanical keyboards. So, a non-portable numeric keyboard implemented via a small, stand-alone touch screen that connected to a traditional computer would encounter the same issues.
The present invention addresses all of these issues on all types of touch screen devices that have virtual keyboards that would otherwise be capable of supporting touch typing.
Prior art exists for touch screen keyboard overlays. However, the prior art does not address the requirements for touch typing on multi-touch, proximity-based touch screens and virtual keyboards such as those found on the iPAD® and similar devices. In fact, many prior art designs prevent touch typing from functioning properly in this environment by blocking the virtual keyboard and its software from accessing vital information about finger position. The software utilizes this position data to maximize its error-correcting facilities. Therefore, by restricting touch input to the visual boundaries of the keys on the virtual keyboard as opposed to expanded touch areas that include the visual borders between keys, many prior art touch screen overlays introduce “dead zones”. These overlays do not allow touch registration from all touch typing finger trajectories, etc.
As described herein, pressure-sensitive and Surface Capacitive touch screens require touch typing users to “bottom out” each key stroke. Thus, all of the features designed to keep this from happening (pre-actuation tactile cueing, finger deceleration, spring-back) are not available in keyboard overlays that are designed for these types of touch screens, since they need the user to bottom out while typing in order to actuate the touch screen. These features are critically important enablers for optimal touch typing.
Keyboard overlays which are designed to transmit pressure from the bottom of the keyboard overlay to a pressure-sensitive touch screen sometimes concentrate this pressure by attaching force directing nibs to the bottom of their key structures. For example, ref. no. 306 in US Patent Application 2003/0235452 shows an exemplary pressure concentrator.
This feature will actually disable proper functioning of a proximity-based touch screen since these nibs will keep the user's fingers too far away from the proximity detection threshold to be registered.
Prior art keyboard overlays often create “dead zones”—regions in the keyboard overlay that impedes a key stroke from registering on a proximity-based touch screen because the user's finger is blocked from getting into proximity by the material that makes up the keyboard overlay, or when a key structure folds over itself when depressed and creates a thick zone that doesn't allow the finger to get into detection proximity.
In some cases these regions are created inadvertently, for example, a keyboard overlay that was designed to be used with pressure-sensitive touch screen would not need to be concerned with “dead zones” since pressure is still transmitted to the pressure-sensitive touch screen. Sometimes they are created by design, with the “dead zone” a part of another feature previously believed to be beneficial.
One example of a “dead zone” is an extra ridge on the perimeter of a key top, as illustrated in ref. no. 308 in US Patent Application 2003/0235452. A ridge of this nature is not a problem for a pressure-sensitive touch screen, since the pressure will be correctly transmitted from the user's finger to the ridge, then to the bottom of the keyboard overlay and then to the pressure-sensitive touch screen. However, it is a major problem for a proximity-based touch screen, since the ridge will keep the user's finger from getting within range of the proximity-based touch screen. An attempted keystroke passed through this overlay will therefore not be registered on a proximity-based touch screen.
Another example of a “dead zone” is a rigid frame that surrounds each key structure on the keyboard overlay, as illustrated in ref no. 314 in US Patent Application 2003/0235452. Such a rigid frame might be required by a keyboard overlay designed to work with a single-point pressure-sensitive touch screen in order to avoid inadvertent pressure interaction between multiple keys. However, it acts as a detriment to proper functioning of a proximity-based touch screen, since the frame keeps valid key strokes from registering. This is especially the case for touch typing, where lateral, (also known as shallow angle) key strokes (both North/South and East/West) will often strike a key at a non-vertical angle and are easily blocked by a rigid frame.
Prior art key structures with thick sidewalls also introduce “dead zones.” These sidewalls do not depress or collapse when a key is pressed, as illustrated in ref no. 300 in US Patent Application No. 2003/0235452. The thick sidewalls interfere with lateral trajectory key strokes and even vertical trajectories when the finger is slightly off-center of the key. These types of key strokes are natural to touch typing, but will not register on a proximity-based touch screen because of the construction of the prior art keyboard overlay.
“Dead zones” are problematic because they cause key strokes to be lost, and interfere with the ability of a modern virtual keyboard's software to correctly perform touch recognition. Multi-point touch screen software detects many points when a finger comes into proximity, and the shape and size of touch locations are analyzed to determine the nature of the touch—was it a finger, the heel of a hand, or an accidental glancing touch that should be ignored? A “dead zone” that is a significant fraction of the finger contact area can cut off a portion of the distinctive shape of a finger press that the software is looking for. Also, modern virtual keyboard software is designed to accept all key strokes and recognize complete words and sentences. So even if a particular key stroke is misrecognized at the character level, the location of the user's finger as detected by the touch screen will be later used as part of word-level recognition and correction. If this information is partially or completely lost because of a keyboard overlay induced “dead zone”, word-level correction will potentially fail completely.
Another problem with the “dead zones” is that modern tablet computers such as the iPAD® and XOOM® allow the user to hold their finger down on the virtual keyboard for a period of time to bring up a menu, which can then only be accessed by keeping their finger in proximity and sliding it over the menu. For example, this is used to display all of the accented variations of a letter (i.e. holding down the “e” key 60 for a period of time will bring up a secondary menu 61 with è, ê, ë, etc.), as shown in FIG. 6. This is impossible to execute if there is a frame or “dead zone” around each key structure or even if, as in this example, the “dead zone” is located only to the north of the virtual key. If the overlay key structure sidewalls are too thick for touch screen registration, or if there is any other “dead zone” on or around the key structure, then this secondary menu functionality will likely be lost.
The key structures and key arrays in the prior art are not designed for effective touch typing. Prior art keyboard overlays often simply copy the visual appearance of the key caps on a conventional keyboard, as illustrated in ref no. 300 in US Patent Application No. 2003/0235452 and ref. no. 401 in US Patent Application No. 2007/0013662. However, these key structures do not provide the appropriate non-linear resistive force, nor enough absolute resistive force over the length of key travel for effective touch typing. These prior art key structures have force displacement curves 65 similar to the one shown in FIG. 7.
In this force displacement curve 65, resistive force increases from zero as the user's finger starts to compress the overlay against the touch screen 66, and rises rapidly as the material in the overlay reaches maximum compression attainable by human generated force 67. There is no pre-actuation tactile cue, no resistive deceleration of the user's finger before it “bottoms-out” against the touch screen's surface, and insignificant spring-back on the return.
Furthermore, this force displacement curve 65 does not allow users to rest their fingers on the home row keys without accidentally triggering the touch screen.
Some prior art keyboard overlays are complex mechanical apparatuses composed of many parts, each of which has to be manufactured and then assembled together, as shown in FIG. 5 in US Patent Application 2010/0302168, and FIG. 4 in Great Britain Patent Application 1996-GB-2313343. These types of keyboard overlays do not actuate the underlying touch screen directly with the user's finger; instead they utilize indirect mechanical means to trigger actuation, typically driven by physical keys with hard key tops. They essentially take a mechanical keyboard assembly, replace the electrical switches with mechanical actuators and position the resulting apparatus on top of a touch screen.
In the case of FIG. 5 in US Patent Application 2010/0302168, the touch screen is triggered by an actuation nib made of conductive material that is fastened to the bottom of a key rod. In the case of FIG. 4 in Great Britain Patent Application 1996-GB-2313343, a system of infrared LEDs and photo detectors is used to register key presses, not the underlying touch screen.
These types of keyboard overlays interfere with the operation of modern virtual keyboard software. This software uses the shape and precise location points that the pad of the user's finger registers on the touch screen for character, word and sentence level analysis. Since these keyboard overlays use mechanisms such as conductive nibs to trigger the touch screen, they will give unexpected location information to the virtual keyboard's software when a user accidentally presses an incorrect key. This will potentially cause the virtual keyboard's software to behave incorrectly.
The following is a review of several prior art keyboard overlay patents that are representative of the different types of prior art:
U.S. Pat. No. 5,572,573 describes a physical overlay that is placed over the touch screen of a mobile phone. The overlay is composed primarily of a material whose desired structural properties are only attainable in wall thicknesses that would block actuation of the touch screen. The overlay contains cut out holes over specific areas of the touch screen, allowing the user to find specific locations on the touch screen without looking at it. The frame of this overlay is a continuous “dead zone” that would not work for touch typing as described above. There are no key structures whatsoever in this design, just a hole, so resting fingers on the home row would actuate all the keys.
U.S. Pat. No. 5,909,211 describes a computer system with multiple replaceable overlays for a touch workpad, including a full-size keyboard overlay. However, these overlays do not contain any key structures, and are therefore unsuitable for touch typing.
U.S. Pat. No. 5,887,995 describes a tactile overlay that goes on top of the single-point capacitive touchpad typically found below the keyboard of a notebook computer. This overlay is composed of a flat, flexible plate with dome-shaped “tactile response elements” attached to the bottom of the plate. It does not have a have force displacement curve appropriate for touch typing and is a complex assembly that does not allow the user to see the underlying indicia. Additionally, the assembly, being made up of a stack of parts will, when structurally capable of providing proper resistive force for touch typing, keep the user's finger tips out of range of detection of the underlying touchscreen. Finally, there are no tactile features on the top surface of the overlay, which makes it unusable for touch typing.
U.S. Pat. No. 6,667,738 describes a tactile overlay for the 10 digit numeric keypad of a cellular phone with a touch screen. The overlay is composed of dome-shaped keys, similar to those described in U.S. Pat. No. 5,887,995. This overlay will also exhibit a force displacement curve similar to that of calculator keys, which isn't appropriate for touch typing.
US Patent Application No. 2003/0235452 (and subsequent U.S. Pat. Nos. 6,776,546, 6,880,998 and 7,659,885) describes a full-size keyboard overlay that that provides location tactile references that enable a user to align their fingers over the keys of a virtual keyboard (however, it does not disclose using sharp key top edges for this purpose, as described herein). This patent describes keyboard overlays designed to be used with pressure-sensitive touch screens, and has all the problems with “dead zones”, pressure concentrators on the bottom of keys, etc. on proximity-based touch screens, as described herein. The key structures disclosed in this patent do not have any of the necessary attributes needed for touch typing, as described herein, nor will they enable users to rest their fingers on the key structures without triggering the underlying touch screen. Their keyboard overlays are designed for a single-point touch screen, not multi-touch, as shown on Page 8 of this patent application, and will therefore not work correctly with modern virtual keyboards, as described herein.
US Patent Application No. 2010-0238119 describes a keyboard overlay and attached case for an iPhone. The key structures described in this patent do not have any of the characteristics required for effective touch typing, as described herein. Also, it is not designed to work on the size (or pitch) of keyboard required for touch typing.
US Patent Application No. 2010/0302168 describes a complex mechanical keyboard overlay consisting of multiple physical keys with hard key tops, actuator rods, etc. The key structures described in this patent do not have any of the characteristics required for effective touch typing, as described herein.
Great Britain Patent Application No. 1996-GB-2313343 describes a complex mechanical keyboard overlay consisting of a see-through hard plastic key array that sits on top of an LCD display (not a touch screen). Infrared LEDs and photo-detectors are used to sense when keys are depressed. The key structures described in this patent do not have any of the characteristics required for effective touch typing, as described herein.